ReBarUEFI

Since I don't want to tinker with my HP Firmware, a brief investigation led me to OpenCore's ability to enable Resizable BAR in the bootloader before Windows boots. Not sure how reliable it is. https://github.com/xCuri0/ReBarUEFI/discussions/118

Can anyone verify if this works on a Lenovo Thinkpad? I checked the List of Working Motherboards [1]. They often have Thunderbolt but no way to enable ReBAR. [1] https://github.com/xCuri0/ReBarUEFI/issues/11

Note that some tinkering may be required for modern cards on old systems. - A UEFI DXE driver to enable Resizable BAR on systems which don't support it officially. This provides performance benefits and is even required for Intel Arc GPUs to function optimally. List of working motherboards https://github.com/xCuri0/ReBarUEFI/issues/11

> In a Linux context I got some GPUs working and I can add some [external] GPU devices. Minis forum when I reached out to them said they don't officially support either via the Thunderbolt compatibility USB 4, USB4 v2 or even the built-in PCIe slot. Yeah, not technically officially supported and it's because of the resource allocation and the BAR space and they need somebody on the BIOS team to understand that to fix it. https://www.youtube.com/watch?v=TvNYpyA1ZGk There are ways to manage BAR better in linux or with UEFI preboot environments for windows as hobbyists have been doing for ages due to bad BIOS support https://github.com/xCuri0/ReBarUEFI

Great project, but emphasis on Almost[0]. It will not work in the one computer where I need it; On Haswell, 32GB RAM + 16GB BAR is currently not possible[1]. 0. https://github.com/xCuri0/ReBarUEFI/wiki/Common-issues-(and-... 1. https://github.com/xCuri0/ReBarUEFI/issues/20

If the firmware is open source, perhaps it could be retrofitted. For amd64 motherboards that do not have native UEFI support, retrofits are possible through this: https://github.com/xCuri0/ReBarUEFI

ReBARUEFI was enough to get it working on an ASUS P8P67-something something when I tried it in January-ish. [1] https://github.com/xCuri0/ReBarUEFI

There is a Github project [1] which has detailed instructions. The ancient i5-3570 only allowed 2GB ReBAR, BTW. GPU-Z says ReBAR / 4G is activated and working, Intel Arc Driver does not see it but seems to use it. Some part of the BIOS had to be manually fixed, AFAIR. The PC was given for free, the CPU €11 yet overall I wouldn't recommend the process just for the result. It's only little benefit, if at all, though fun. On that occasion I also added some NVMe driver which works well, demonstrated for the similar Dell Optiplex [2][3].. [1] https://github.com/xcuri0/rebaruefi [2] https://www.tachytelic.net/2021/12/dell-optiplex-7010-pcie-n... [3] https://github.com/jrdoughty/Dell-7010-rebar-guide Edit: some wording

Yeah, there were also efforts like this, too https://github.com/xCuri0/ReBarUEFI Given that I got an Intel Arc A580 for myself, this was pretty important! Quite bad that it wasn't officially supported if there are no hardware issues and I would have liked to just keep using the 1700 for a few more years, but opted for just buying a new CPU so my old one would be a reasonable backup, path of least resistance in this case. Would also like to try out the recent Intel CPUs (though surely not the variety that seems to have stability issues), but that's not in the cards for now because most of my PCs and homelab all use AM4, on which I'll stay for the foreseeable future.